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Jabiru temps
I'm having a really bad time getting my CHT and EGT temps down in my Jabiru 3300. I did a lot of work on adding an extension to the lower cowl lip and adding a "fence" above various cylinders to move air back toward the rear of the ram air ducts. I had moderate success prior to early April, but then went to Ireland for 2 weeks and returned to outside air temps that were 40 degrees warmer than when I flew last.
Naturally, now my CHT and EGT temps are way too high. CHT's are high on #3 and #5 and EGT's are high on #5 and #6.
Today, I enlarged the Needle Jet from 2.85 to 2.90 mm and go some better numbers, but only could stay in the air for @ 5 minutes before the CHT's got dangerous, so I don't know how high the EGT's would have gone if I had flown longer?
I was turning 3160 rpm at 70 mph climb-out.
Replies to This Discussion
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Permalink Reply by Ian McClelland on
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Hi Edward. I have a Jabiru 3300 installed into a 601XL so your numbers look odd to me.
Is 3160 RPM for a 70 mph climb in a 750 normal for the type? The RPM seems high.
I have 2900 RPM for a 85 knot climb and 140 deg C CHT's.
Is the Engine new?
Will it cool down during a straight and level cruise?
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Permalink Reply by Bob McDonald on
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Ian
The Jabiru 3300 is a "Happy Camper" in the fast low drag airframe of the CH601XL-B. In the high drag (engine works harder), low airspeed (low cooling) of the CH750 airframe it is a totally different engine. I have flown both airframes back to back in the test flight stage and the Jabiru 3300 in the CH750 was a nightmare compared to the engine performance in the CH601XL-B.
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Permalink Reply by Dr. Edward L. Olds III on
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Bob,
Roger that, it is a nightmare!! Back to the airport and some more stumbling around!
Ed
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Permalink Reply by John Austin on
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Hmmm ... my 750/3300 "nightmare" runs about 192F oil temps and CHT's of 215-286F, cruises at 80 kts, and burns 6.2 gph, is smoother than my Mom's Singer, and has the coolest sound short of a Merlin ... and doesn't sound like a Rotax lawnmower!
Sweet Dreams, Bob! LOL!
John
N750A
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Ian,
I don't know if 3160 is high, but it is what I'm getting. Pete at Jabiru was surprised, I think? The engine has only @ 20 hours tach time, but it will not cool in cruise!
Ed
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Permalink Reply by Andre Levesque on
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Hi Ed,
You may want to look at http://www.rotecaerosport.com/products/lch/ -:)
Not a cheap option but could be an alternative I guess.
So frustrating to pay so much$$$ for an engine and have all those cooling problems.
Can't Zenith help you out with those issues?? They had a jabiru 3300 in a ch750 for a longtime.
Bob has a point with the 750 as a higher drag aircraft but many 750's are running jabiru 3300 quite successfully including Zenith themselves. Although they seem to have switched from Rotax to Jabiru to the ULpower engines they should be able to provide guidnace on the FWF cooling for the Jab 3300.
Hang in there.
Andre
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I wouldn't spend thousands on liquid cooled heads that also introduce multiple additional failure modes (liquid cooling leaks in pipes or radiator, dependence on an electrical pump for coolant circulation, etc.) on an engine that isn't even broken-in. Cooling the Jab needs to follow a logical, step-wise process. It's certainly not "plug and play", but it's been kind of fun tweaking it ... sort of like building your own airplane!
My personal opinion is that about half of any temp improvement will result from the tweaks and the other half will result from the engine finally being actually broken-in by the time the last tweak is done!
I will admit, however, that I think engines after #2331 with the increased cylinder head fin area and new plenum,diffusers, and intake runners for more even mixture distribution are probably easier to tame.
I'm now at 137 hrs with zero engine issues - just put gas in the tank, start it, and fly!
John
N750A
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Hummm you are probably right!! I for one do not like too many hoses on an engine -:)
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Andre,
Yes frustrating is a mold term for having these problems. My mother-in-law was hospitalized today, so I'm on hold for awhile.
Ed
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Ian - Just for reference, I can pull about 3100 (Sen. wood prop) in climbout, but I'm usually doing about 45 kts/52 mph and 700 fpm. Highest cylinder temp is 302F in climb, the rest mid-upper 200's F (with an ambient of about 70F).
John
N750A
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You may like to consider installing a cowl flap as I have done. I have done this as I have an older engine with small fin heads and wanted more control over the amount of cooling air being drawn through the engine.
It has not been fully tested yet but early results are promising. I have cooler CHT,s on taxi and climb and can reduce cooling slightly from standard for the long high speed descents. I have added more photos on my page. .
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